Note that a variety of PaaS tailored for developers of mobile applications generally goes by the name of MBaaS (mobile back end as a service), or sometimes just BaaS (back end as a service).
FaaS (functions as a service)
FaaS, the cloud instantiation of serverless computing, adds another layer of abstraction to PaaS, so that developers are completely insulated from everything in the stack below their code. Instead of futzing with virtual servers, containers, and application runtimes, they upload narrowly functional blocks of code, and set them to be triggered by a certain event (e.g. a form submission or uploaded file). All the major clouds offer FaaS on top of IaaS: AWS Lambda, Azure Functions, Google Cloud Functions, and IBM OpenWhisk. A special benefit of FaaS applications is that they consume no IaaS resources until an event occurs, reducing pay-per-use fees.
The private cloud downsizes the technologies used to run IaaS public clouds into software that can be deployed and operated in a customer’s data center. As with a public cloud, internal customers can provision their own virtual resources in order to build, test, and run applications, with metering to charge back departments for resource consumption. For administrators, the private cloud amounts to the ultimate in data center automation, minimizing manual provisioning and management. VMware’s Software Defined Data Center stack is the most popular commercial private cloud software, while OpenStack is the open source leader.
A hybrid cloud is the integration of a private cloud with a public cloud. At its most developed, the hybrid cloud involves creating parallel environments in which applications can move easily between private and public clouds. In other instances, databases may stay in the customer data center and integrate with public cloud applications—or virtualized data center workloads may be replicated to the cloud during times of peak demand. The types of integrations between private and public cloud vary widely, but they must be extensive to earn a hybrid cloud designation.
Public APIs (application programming interfaces)
Just as SaaS delivers applications to users over the internet, public APIs offer developers application functionality that can be accessed programmatically. For example, in building web applications, developers often tap into Google Maps’ API to provide driving directions; to integrate with social media, developers may call upon APIs maintained by Twitter, Facebook, or LinkedIn. Twilio has built a successful business dedicated to delivering telephony and messaging services via public APIs. Ultimately, any business can provision its own public APIs to enable customers to consume data or access application functionality.
iPaaS (integration platform as a service)
Data integration is a key issue for any sizeable company, but particularly for those that adopt SaaS at scale. iPaaS providers typically offer prebuilt connectors for sharing data among popular SaaS applications and on-premises enterprise applications, though providers may focus more or less on B-to-B and ecommerce integrations, cloud integrations, or traditional SOA-style integrations. iPaaS offerings in the cloud from such providers as Dell Boomi, Informatica, MuleSoft, and SnapLogic also enable users to implement data mapping, transformations, and workflows as part of the integration-building process.
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